|   Decompression | Swerd
Apr 18, 2003 9:27 AM | | A number of years ago, I experienced something unexpected and different in home audio. It was the first time I heard a demonstration of the effect of dynamic range expansion. I had a friend and his wife over for dinner one Saturday. Like myself, he also was a young audio enthusiast. We had friendly debates over the benefits of high-powered amplifiers. I maintained that as long as an amplifier was sufficiently powerful to drive speakers of a given efficiency it didn't matter much unless you wanted to fill a large theater with sound. He of course said high-powered amps made a big difference even in normal sized rooms.
That evening in 1979, he knew my stereo receiver was in the shop and no music would be available that night. Because he liked my speakers, he surprised me by lugging his Phase Linear preamp and amplifier over. I don't remember what models they were. I believe the amplifier produced 200 watts per channel, and I remember being told they were made in the mid 1970s before Pioneer purchased the line. My receiver, a Marantz 2230, was a medium quality 30 watt per channel Japanese solid-state receiver. This was a great opportunity for me to listen to familiar music in my living room, coming from my speakers driven by this premium gear.
One aspect of my speakers that I had always liked was they created the illusion that music came from various places in the room rather than only from the speaker boxes. My first impression that night with the Phase Linear gear was that the music sounded somewhat more out-of-the-box than I had heard before.
Later that evening, after dinner, when I paid more attention to the stereo, I noticed a knob on the preamp labeled Decompression. At the time it was turned most of the way up. When I turned it down, I was stunned to hear the music retreat back into the speaker boxes. The volume seemed the same, but it was as if a vacuum had sucked up the musicians into the speakers. I quickly turned the knob back up and they returned to the places out in the room where they were before. I had heard large audible differences among different speakers, but I had never heard such a large audible difference coming from electronic gear. I loved the effect that Decompression knob had.
I have to be honest. I don't know if the nearly 7-fold increase in amplifier power had anything to do with this fascinating effect. It seemed to come entirely from the preamp.
This was a time in home audio when improved noise reduction was the latest thing. Dolby Labs already had Dolby B and would soon have Dolby C for tape recording, and DBX made a variety of noise reduction products for tape recording and for dynamic range expansion of any sound source that had been compressed in the recording process. I briefly thought about buying a DBX dynamic range expander, but they were expensive, and I was a poor graduate student. Perhaps when digital recording and CDs came along much of this was abandoned.
My question is what did that decompression knob on the Phase Linear preamp do? Is there anything available now that can do something similar? |
| re: Decompression | jimmymagick
Apr 21, 2003 8:49 AM | | I'm not quite certain if this is what you're referring to but I still have packed away in a box somewhere an outboard unit called the "Phase Linear Model 180 Dimensional Sonic Localizer."
I googled it and this is what I came up with:
"The Model Dimensional Sonic Localizer had essentially the same circuit as the "Ambience" circuit in the 2000 preamp. It put a variable amount of L-R on one channel and L+R on the other. The front of the unit stated it was the Dimensional Sonic Locator Model 180 while the back stated Model 180 Sound Imager."
I remember being at a local stereo dealer here in Chicago and when he demoed it for me, I just had to have it. (And I remember the price was something like $125.) Worked very nicely on vinyl but I seem to recall that the effect on well-recorded CD's was considerably less dramatic. That's why it's currently retired (along with Powered Partners speakers, Dolby Pro Logic Unit and all the other remnants of 25 years of trying to upgrade my stereo.) |
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